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// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "components/services/storage/indexed_db/scopes/varint_coding.h"
#include <array>
#include "base/check_op.h"
namespace content::indexed_db {
void EncodeVarInt(int64_t from, std::string* into) {
DCHECK_GE(from, 0);
// A temporary array is used to amortize the costs of the string modification.
static constexpr size_t kMaxBytesForUInt64VarInt = 10;
std::array<char, kMaxBytesForUInt64VarInt> temp;
uint64_t n = static_cast<uint64_t>(from);
size_t temp_index = 0;
do {
unsigned char c = n & 0x7f;
n >>= 7;
if (n)
c |= 0x80;
DCHECK_LT(temp_index, kMaxBytesForUInt64VarInt);
temp[temp_index] = c;
++temp_index;
} while (n);
into->append(temp.data(), temp_index);
}
bool DecodeVarInt(std::string_view* from, int64_t* into) {
std::string_view::const_iterator it = from->begin();
int shift = 0;
uint64_t ret = 0;
do {
// Shifting 64 or more bits is undefined behavior.
if (it == from->end() || shift >= 64)
return false;
unsigned char c = *it;
ret |= static_cast<uint64_t>(c & 0x7f) << shift;
shift += 7;
} while (*it++ & 0x80);
*into = static_cast<int64_t>(ret);
from->remove_prefix(it - from->begin());
return true;
}
} // namespace content::indexed_db
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